The machining of parts involving chip removal is often performed by a modular tool system in which the part carrying the cutting bit is separated from the tool carrier (spindle or revolver) by a suitable coupling, sometimes with the interposition of an adapter and/or a reduction gear. The couplings often include cylinders (with planar contact faces) or cones. Couplings equipped with one or a plurality of cones may be self-locking and cylinders having planar contact faces may adhere to one another and therefore not only a clamping force, but also an oppositely oriented releasing force is needed.
German Pat. No. 3,108,439 discloses a drilling tool whose shank terminates in a cylindrical coupling stub and is surrounded by an annular shoulder extending perpendicularly to the axis of the drilling tool. The coupling stub is provided with a transverse bore and a connecting pin displaceable therein. The connecting pin has a conical projection or a conical recess at both ends. Coaxially with a radial clamping screw provided in the tool holder and diametrically opposite thereto, the tool holder supports a further identical radial clamping screw. If one screw is tightened, the connecting pin is displaced in the transverse bore until it is supported at the oppositely disposed cone of the other screw. As a result of this arrangement, identical forces act on both ends of the connecting pin. Due to the conical configuration of the connecting pin at both ends, axial forces are generated by camming action, producing a satisfactory clamping of the annular shoulder surfaces against those provided on the tool holder.
German Offenlegungsschrift (non-examined published application) No. 3,532,891 to which corresponds U.S. application Ser. No. 06/907,084 to Von Haas filed September 12, 1986 discloses a coupling connection without play. The connection is composed of an axial planar contact face, a short cone and a cylindrical terminal pin. This coupling connection can be tightened with the previously-described type of clamping arrangement. However, the coupling connection cannot be released by means of the holding (clamping) screws if the cone is self-locking.